Apparatus for depositing thin films using hydrogen peroxide

ABSTRACT

A thin film deposition system is disclosed in order to form a thin film on a substrate. The thin film deposition system comprises a hydrogen peroxide source. The hydrogen peroxide source comprises an electrochemical cell that converts a hydrogen gas to a hydrogen ion gas. The electrochemical cell converts an oxygen gas and water into a liquid phase complex. The liquid phase complex reacts with the hydrogen ion gas to form hydrogen peroxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Nonprovisional of, and claims priority to and thebenefit of, U.S. Provisional Patent Application No. 63/029,210, filedMay 22, 2020 and entitled “APPARATUS FOR DEPOSITING THIN FILMS USINGHYDROGEN PEROXIDE,” which is hereby incorporated by reference herein.

FIELD OF INVENTION

The invention relates to a reaction system for processing semiconductorsubstrates. Specifically, the invention relates to a reaction systemused for depositing an oxide film with hydrogen peroxide as an oxygensource.

BACKGROUND OF THE DISCLOSURE

Atomic layer deposition (ALD) processes may be used to deposit thinfilms onto semiconductor substrates. Such thin films may includezirconium oxide, titanium oxide, tin oxide, aluminum oxide, hafniumoxide, silicon oxide, and any mixtures thereof. When forming particularthin films with an oxygen component such as an oxide or an oxynitride,an oxygen-containing precursor may be employed.

The oxygen-containing precursor may be water, ozone, or oxygen plasma.Ozone and oxygen plasma may be stronger oxidizers than water, but eachhas issues that affect its ability to enable formation of the thinfilms. Ozone, for example, lacks hydrogen atoms that further assist inremoving ligands from a growing thin film. Oxygen plasma may have theside effect of damaging the surface; this may lead to a reduced abilityto coat high aspect ratio features.

Hydrogen peroxide may make up for the deficiencies from ozone or oxygenplasma, as it is a stronger oxidizer than water while providing thehydrogen atoms that ozone lacks. Hydrogen peroxide also does not damagethe surface in the same manner as oxygen plasma. However, hydrogenperoxide suffers from decomposition during storage.

However, prior approaches to generate hydrogen peroxide havedeficiencies. U.S. Pat. No. 6,767,447 discloses an electrochemical cellutilizing a sodium sulphate solution as an electrolyte. Utilizing saltsolutions as an electrolyte is undesirable because of particlesgenerated leading to wafer contamination. U.S. Pat. No. 6,712,949discloses an approach using ion membranes to separate electrodes whengenerating hydrogen peroxide from an acidic electrolyte formed fromsulphuric acid. Detrimental aspects of sulphuric acid stem from theformation of aerosol particles of either the acid or produced salts,thereby creating particulate defects on the processed wafer. Thecorrosive nature of any such material carried downstream can also damagereactor components or wafers under production.

U.S. Pat. No. 5,972,196 discloses an electrochemical cell for theproduction of ozone. The ozone then decomposes in water to producehydrogen peroxide. The decomposition of ozone requires significantcontrol in order to maintain consistent doses of hydrogen peroxide. Inaddition, the use of ozone is problematic for the reason describedbefore, that ozone lacks hydrogen atoms that further assist in removingligands from a growing thin film.

As a result, a need exists for a system that generates hydrogen peroxidefor growing thin films while avoiding the issue of decomposition.

SUMMARY OF THE DISCLOSURE

In at least one embodiment of the invention, a reaction systemconfigured to form a thin film on a substrate is disclosed. The reactionsystem comprises: a reaction chamber configured to hold a substrate tobe processed; a first precursor source, the first precursor sourceconfigured to provide a first precursor gas to the substrate; an inertgas source, the inert gas source configured to provide an inert gas tothe substrate; and a hydrogen peroxide source configured to provide ondemand a liquid hydrogen peroxide solution, wherein the hydrogenperoxide source comprises: an electrochemical cell comprising: a porouselectrolyte, a first gas diffusion layer, a second gas diffusion layer,a catalyst layer, an activated carbon layer, a first membrane layer, anda second membrane layer; a hydrogen source, the hydrogen sourceconfigured to provide a hydrogen gas, wherein the hydrogen gas passesthrough the first gas diffusion layer, the catalyst layer, and the firstmembrane layer into the porous electrolyte; an oxygen source, the oxygensource configured to provide an oxygen gas, wherein the oxygen gaspasses through the second gas diffusion layer, the activated carbonlayer, and the second membrane layer into the porous electrolyte; and awater source, the water source configured to provide water to the porouselectrolyte; wherein the catalyst layer converts the hydrogen gas into ahydrogen ion (H⁺) gas; and wherein the activated carbon layer convertsthe oxygen gas into an ion that reacts with the water in the porouselectrolyte to form a liquid phase (HO₂ ⁻) complex.

In at least one embodiment of the invention, a reaction systemconfigured to form a thin film on a substrate is disclosed. The reactionsystem comprises: a reaction chamber configured to hold a substrate tobe processed; a first precursor source, the first precursor sourceconfigured to provide a first precursor gas to the substrate; an inertgas source, the inert gas source configured to provide an inert gas tothe substrate; and a hydrogen peroxide source configured to provide ondemand a liquid hydrogen peroxide solution, wherein the hydrogenperoxide source comprises: an electrochemical cell comprising: a porouselectrolyte, a first gas diffusion layer, a second gas diffusion layer,a catalyst layer, an activated carbon layer, a first membrane layer, anda second membrane layer; a hydrogen source, the hydrogen sourceconfigured to provide a hydrogen gas, wherein the hydrogen gas passesthrough the first gas diffusion layer, the catalyst layer, and the firstmembrane layer into the porous electrolyte; an oxygen source, the oxygensource configured to provide an oxygen gas, wherein the oxygen gaspasses through the second gas diffusion layer, the activated carbonlayer, and the second membrane layer into the porous electrolyte; and anitrogen source, the nitrogen source configured to provide a nitrogen(N₂) gas to the porous electrolyte; wherein the catalyst layer convertsthe hydrogen gas into a hydrogen ion (H⁺) gas; and wherein the activatedcarbon layer converts the oxygen gas into an ion that forms a liquidphase (HO₂ ⁻) complex.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

These and other features, aspects, and advantages of the inventiondisclosed herein are described below with reference to the drawings ofcertain embodiments, which are intended to illustrate and not to limitthe invention.

FIG. 1 illustrates a thin film deposition system in accordance with atleast one embodiment of the invention.

FIG. 2 illustrates a hydrogen peroxide generator for use in the thinfilm deposition system in accordance with at least one embodiment of theinvention.

FIG. 3 illustrates a hydrogen peroxide generator for use in the thinfilm deposition system in accordance with at least one embodiment of theinvention.

FIG. 4 illustrates a thin film deposition system in accordance with atleast one embodiment of the invention.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help improve understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used, or upon which, a device, acircuit, or a film may be formed.

As used herein, the term “chemical vapor deposition” may refer to anyprocess wherein a substrate is sequentially exposed to one or morevolatile precursors, which react and/or decompose on a substrate toproduce a desired deposition.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, preferably aplurality of consecutive deposition cycles, are conducted in a reactionchamber. Typically, during each cycle the precursor is chemisorbed to adeposition surface (e.g., a substrate surface or a previously depositedunderlying surface such as material from a previous ALD cycle), forminga monolayer or sub-monolayer that does not readily react with additionalprecursor (i.e., a self-limiting reaction). Thereafter, if necessary, areactant (e.g., another precursor or reaction gas) may subsequently beintroduced into the process chamber for use in converting thechemisorbed precursor to the desired material on the deposition surface.Typically, this reactant is capable of further reaction with theprecursor. Further, purging steps may also be utilized during each cycleto remove excess precursor from the process chamber and/or remove excessreactant and/or reaction byproducts from the process chamber afterconversion of the chemisorbed precursor. Further, the term “atomic layerdeposition,” as used herein, is also meant to include processesdesignated by related terms such as, “chemical vapor atomic layerdeposition,” “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor composition(s), reactivegas, and purge (e.g., inert carrier) gas.

As used herein, the term “film” and “thin film” may refer to anycontinuous or non-continuous structures and material formed by themethods disclosed herein. For example, “film” and “thin film” couldinclude 2D materials, nanolaminates, nanorods, nanotubes, ornanoparticles, or even partial or full molecular layers, or partial orfull atomic layers or clusters of atoms and/or molecules. “Film” and“thin film” may comprise material or a layer with pinholes, but still beat least partially continuous.

Embodiments of the invention are directed towards a system fordepositing a thin film through chemical vapor deposition or ALDprocesses. FIG. 1 illustrates a thin film deposition system 100 inaccordance with at least one embodiment of the invention. The thin filmdeposition system 100 may comprise: a reaction chamber 110; a substrateholder 110A configured to hold a substrate; a gas distribution system110B configured to evenly distribute a gas flown into the reactionchamber 110 across the substrate; a hydrogen peroxide source 120; afirst precursor source 130; and an inert gas source 140.

The reaction chamber 110 is shown to have a showerhead arrangement todistribute the gases across the substrate; however, the reaction chamber110 may comprise alternatively one of: a batch reactor with an injectortube system; a cross-flow reactor; or a spatial reactor.

The first precursor source 130 may flow a first precursor gas thatcomprises at least one of: a silicon precursor, such as silane,disilane, trisilane, chlorosilane, dichlorosilane, trichlorosilane,tetrachlorosilane, or tetraethylorthosilicate; a titanium precursor,such as titanium tetrachloride (TiCl₄), titanium tetraalkoxides, ortitanium tetra alkylamides; an indium precursor, such astrimethylindium, triethylindium, or tripropylindium; a molybdenumprecursor, such as molybdenum halides or molybdenum alkylamides; avanadium precursor, such as vanadium halides or vanadium alkylamides; ahafnium precursor, such as hafnium chloride, hafnium alkylamides,cyclopentadienyl hafnium, cyclopentadienyl hafnium alkylamides, orhafnium alkoxides; a zirconium precursor, such as zirconium chloride,zirconium alkylamides, cyclopentadienyl zirconium, cyclopentadienylzirconium alkylamides, or zirconium alkoxides; a lanthanum precursor,such as lanthanum β-diketonates, lanthanum alkylamide, lanthanumacetamidinates, or cyclopentadienyl lanthanum; an aluminium precursor,such as trimethyl aluminium, triethyl aluminium, tripropyl aluminium,tributyl aluminium, aluminium chloride, or aluminium alkoxides. Theinert gas source 140 may flow an inert gas that comprises at least oneof: argon (Ar); xenon (Xe); krypton (Kr); helium (He); or nitrogen (N₂).

The first precursor source 130 and the inert gas source 140 are shown toflow gases that combine in a line outside the reaction chamber 110,while the hydrogen peroxide source 120 flows hydrogen peroxide directlyinto the reaction chamber 110. However, other arrangements are possible,such as having all three gas sources combine into a line outside thereaction chamber or having an additional second inert gas source combinewith the hydrogen peroxide source 120.

The hydrogen peroxide source 120 may also be used in the thin filmdeposition system 100 for other purposes than depositing a thin film.The hydrogen peroxide source 120 may also be used in processes, such aspassivating oxides, spin-on dielectrics, surface cleans, surfaceoxidations, or chemical oxidation. Examples of the hydrogen peroxidesource 120 have been described in a paper entitled “DirectElectrosynthesis of Pure Aqueous H₂O₂ Solutions Up to 20% by WeightUsing a Solid Electrolyte,” published in the journal Science by Xia etal.

FIG. 2 illustrates a hydrogen peroxide source 200 in accordance with atleast one embodiment of the invention. The hydrogen peroxide source 200may comprise: a hydrogen source 210; a water source 220; an oxygensource 230; a porous solid electrolyte 240; a first gas diffusion layer250A; a second gas diffusion layer 250B; an iridium oxide or aplatinum-supported carbon catalyst 260A; an activated carbon layer 260B;a first membrane layer 270A; a second membrane layer 270B; and ahydrogen peroxide output vessel 280.

The hydrogen source 210 provides a hydrogen gas that passes through thefirst gas diffusion layer 250A. The hydrogen gas reaches the iridiumoxide catalyst 260A, which converts the hydrogen gas to a hydrogen ion(H⁺) gas. The H⁺ gas passes through the first membrane layer 270A intothe porous solid electrolyte 240. The porous solid electrolyte 240 maycomprise a polymer such as a styrene-divinylbenzene sulphonatedco-polymer, a Dowex resin, a yttrium-stabilized zirconia, or aninorganic solid such as mixed cesium oxide-tungsten phosphate.

The water source 220 provides liquid water into the porous solidelectrolyte 240. The oxygen source 230 provides an oxygen gas (02) thatpasses through the second gas diffusion layer 250B into the activatedcarbon layer 260B. The oxygen gas is transformed into an ionic form,such that it passes through the second membrane layer 270B and contactsthe water in the porous solid electrolyte 240, thus forming a liquidphase transport (HO₂ ⁻) complex. The HO₂-complex reacts with the H⁺ gasin the porous solid electrolyte 240 to form a H₂O₂ solution that getsstored into the hydrogen peroxide output vessel 280.

The H₂O₂ solution can be generated on demand to provide a constantconcentration of hydrogen peroxide to the reaction chamber 110. Thiswould prevent the hydrogen peroxide stored in the hydrogen peroxideoutput vessel 280 from being stored for too long and result in thedecomposition issues.

FIG. 3 illustrates a hydrogen peroxide source 300 in accordance with atleast one embodiment of the invention. The hydrogen peroxide source 300may comprise: a hydrogen source 310; a nitrogen source 320; an oxygensource 330; a porous solid electrolyte 340; a first gas diffusion layer350A; a second gas diffusion layer 350B; an iridium oxide or aplatinum-supported catalyst 360A; an activated carbon layer 360B; afirst membrane layer 370A; a second membrane layer 370B; and a hydrogenperoxide output 380.

The hydrogen source 310 provides a hydrogen gas that passes through thefirst gas diffusion layer 350A. The hydrogen gas reaches the iridiumoxide catalyst 260A, which converts the hydrogen gas to a hydrogen ion(H⁺) gas. The H⁺ gas passes through the first membrane layer 370A intothe porous solid electrolyte 340. The porous solid electrolyte 340 maycomprise a polymer such as a styrene-divinylbenzene sulphonatedco-polymer, a Dowex resin, a yttrium-stabilized zirconia, or aninorganic solid such as mixed cesium oxide-tungsten phosphate.

The nitrogen source 320 in the hydrogen peroxide source 300 replaces thewater source 220 in the hydrogen peroxide source 200. The nitrogensource 320 may be coupled to a water source to saturate the nitrogenwith water vapor. This distinguishes the hydrogen peroxide source 300from the hydrogen peroxide source 200. The hydrogen peroxide source 200produces an aqueous H₂O₂ solution. The water component of the aqueousH₂O₂ solution may need to be removed before the H₂O₂ is used to depositthin films. The nitrogen source 320 may sidestep this water removalrequirement.

The nitrogen source 320 may provide heated nitrogen (N₂) gas saturatedwith water vapor into the porous solid electrolyte 340. The water vapormay condense into liquid water, which assists in forming the liquidphase transport.

The oxygen source 330 provides an oxygen gas (02) that passes throughthe second gas diffusion layer 350B into the activated carbon layer360B. The oxygen gas is transformed into an ionic form, such that itpasses through the second membrane layer 370B and contacts the condensedliquid water in the porous solid electrolyte 340, thus forming a liquidphase transport (HO₂ ⁻) complex. The HO₂ ⁻ complex reacts with the H⁺gas in the porous solid electrolyte 340 to form a mixture of a H₂O₂vapor and a gas-phase water. This mixture may be consistent, obviatingthe need for a vessel at the hydrogen peroxide output 380. Such mayremove the storage need and peroxide concentration fluctuations fromstarting and stopping operation of the hydrogen peroxide source 300.

In another embodiment in accordance with the invention, the hydrogenperoxide source 300 comprises the nitrogen source 320. The nitrogensource 320 provides a dry nitrogen (N₂) gas and a non-aqueous liquidphase. The non-aqueous liquid phase comprises a liquid with a very lowvapor pressure and a high dipole moment, such as dimethyl sulfoxide(DMSO) or various ionic liquids. This obviates the need for water as asource into the hydrogen peroxide source 300.

Due to the presence of the N₂ gas from the nitrogen source 320, the H₂O₂vapor formed is anhydrous. The liquid has a very low vapor pressure anda high dipole moment. The low vapor pressure reduces loss of the H₂O₂solution to evaporation. The high dipole moment enables dissolution anddiffusion of ionic species generated by the electrode within thehydrogen peroxide source 320. The ionic species allows for recombinationof the H⁺ gas and the HO₂-complex into hydrogen peroxide.

FIG. 4 illustrates a thin film deposition system 400 in accordance withat least one embodiment of the invention. The thin film depositionsystem 400 may comprise: a reaction chamber 410; a substrate holder 410Aconfigured to hold a substrate; a gas distribution system 410Bconfigured to evenly distribute a gas flown into the reaction chamber410 across the substrate; a hydrogen peroxide source 420; a firstprecursor source 430; a second precursor source 440; and an inert gassource 450. The hydrogen peroxide source 420 may be used in this systemto treat a surface of the substrate (such as cleaning or passivatingtreatments, for example) or to clean an interior of the reaction chamber410.

The reaction chamber 410 is shown to have a showerhead arrangement todistribute the gases across the substrate; however, the reaction chamber410 may comprise alternatively one of: a batch reactor with an injectortube system; a cross-flow reactor; or a spatial reactor.

The first precursor source 430 may flow a first precursor gas thatcomprises at least one of: a silicon precursor, such as silane,disilane, trisilane, chlorosilane, dichlorosilane, trichlorosilane,tetrachlorosilane, or tetraethylorthosilicate; a titanium precursor,such as titanium tetrachloride (TiCl₄), titanium tetraalkoxides, ortitanium tetra aklylamides; an indium precursor, such astrimethylindium, triethylindium, or tripropylindium; a molybdenumprecursor, such as molybdenum halides or molybdenum alkylamides; avanadium precursor, such as vanadium halides or vanadium alkylamides; ahafnium precursor, such as hafnium chloride, hafnium alkylamides,cyclopentadienyl hafnium, cyclopentadienyl hafnium alkylamides, orhafnium alkoxides; a zirconium precursor, such as zirconium chloride,zirconium alkylamides, cyclopentadienyl zirconium, cyclopentadienylzirconium alkylamides, or zirconium alkoxides; a lanthanum precursor,such as lanthanum β-diketonates, lanthanum alkylamide, lanthanumacetamidinates, or cyclopentadienyl lanthanum; an aluminium precursor,such as trimethyl aluminium, triethyl aluminium, tripropyl aluminium,tributyl aluminium, aluminium chloride, or aluminium alkoxides.

The second precursor source 440 may provide a nitrogen gas (should anitride film be formed) or an oxygen gas (should an oxide film beformed). The inert gas source 450 may flow an inert gas that comprisesat least one of: argon (Ar); xenon (Xe); krypton (Kr); helium (He); ornitrogen (N₂).

The first precursor source 430, the second precursor source 440, and theinert gas source 450 are shown to flow gases that combine in a lineoutside the reaction chamber 410, while the hydrogen peroxide source 420flows hydrogen peroxide directly into the reaction chamber 410. However,other arrangements are possible, such as having all three gas sourcescombine into a line outside the reaction chamber or having an additionalsecond inert gas source combine with the hydrogen peroxide source 420.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. Thus, the various acts illustrated may beperformed in the sequence illustrated, in other sequences, or omitted insome cases.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems, and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

What is claimed is:
 1. A reaction system configured to form a thin filmon a substrate, comprising: a reaction chamber configured to hold asubstrate to be processed; a first precursor source, the first precursorsource configured to provide a first precursor gas to the substrate; aninert gas source, the inert gas source configured to provide an inertgas to the substrate; and a hydrogen peroxide source configured toprovide on demand a liquid hydrogen peroxide solution, wherein thehydrogen peroxide source comprises: an electrochemical cell comprising:a porous electrolyte, a first gas diffusion layer, a second gasdiffusion layer, a catalyst layer, an activated carbon layer, a firstmembrane layer, and a second membrane layer; a hydrogen source, thehydrogen source configured to provide a hydrogen gas, wherein thehydrogen gas passes through the first gas diffusion layer, the catalystlayer, and the first membrane layer into the porous electrolyte; anoxygen source, the oxygen source configured to provide an oxygen gas,wherein the oxygen gas passes through the second gas diffusion layer,the activated carbon layer, and the second membrane layer into theporous electrolyte; and a water source, the water source configured toprovide water to the porous electrolyte; wherein the catalyst layerconverts the hydrogen gas into a hydrogen ion (H⁺) gas; and wherein theactivated carbon layer converts the oxygen gas into an ion that reactswith the water in the porous electrolyte to form a liquid phase (HO₂ ⁻)complex.
 2. The reaction system of claim 1, wherein the porouselectrolyte comprises at least one of: a styrene-divinylbenzenesulphonated co-polymer, a Dowex resin, a yttrium-stabilized zirconia, aninorganic solid, or a mixed cesium oxide-tungsten phosphate.
 3. Thereaction system of claim 1, wherein the catalyst layer comprises atleast one of: iridium oxide, or a platinum-supported carbon.
 4. Areaction system configured to form a thin film on a substrate,comprising: a reaction chamber configured to hold a substrate to beprocessed; a first precursor source, the first precursor sourceconfigured to provide a first precursor gas to the substrate; an inertgas source, the inert gas source configured to provide an inert gas tothe substrate; and a hydrogen peroxide source configured to provide ondemand a liquid hydrogen peroxide solution, wherein the hydrogenperoxide source comprises: an electrochemical cell comprising: a porouselectrolyte, a first gas diffusion layer, a second gas diffusion layer,a catalyst layer, an activated carbon layer, a first membrane layer, anda second membrane layer; a hydrogen source, the hydrogen sourceconfigured to provide a hydrogen gas, wherein the hydrogen gas passesthrough the first gas diffusion layer, the catalyst layer, and the firstmembrane layer into the porous electrolyte; an oxygen source, the oxygensource configured to provide an oxygen gas, wherein the oxygen gaspasses through the second gas diffusion layer, the activated carbonlayer, and the second membrane layer into the porous electrolyte; and anitrogen source, the nitrogen source configured to provide a nitrogen(N₂) gas to the porous electrolyte; wherein the catalyst layer convertsthe hydrogen gas into a hydrogen ion (H⁺) gas; and wherein the activatedcarbon layer converts the oxygen gas into an ion that forms a liquidphase (HO₂ ⁻) complex.
 5. The reaction system of claim 3, wherein theporous electrolyte comprises at least one of: a styrene-divinylbenzenesulphonated co-polymer, a Dowex resin, a yttrium-stabilized zirconia, aninorganic solid, or a mixed cesium oxide-tungsten phosphate.
 6. Thereaction system of claim 3, wherein the catalyst layer comprises atleast one of: iridium oxide, or a platinum-supported carbon.
 7. Thereaction system of claim 3, wherein the nitrogen source further providesa water vapor with the nitrogen gas.
 8. The reaction system of claim 3,wherein the nitrogen source further provides a non-aqueous liquid withthe nitrogen gas.
 9. The reaction system of claim 8, wherein thenon-aqueous liquid comprises at least one of: dimethyl sulfoxide (DMSO)or an ionic liquid.